Add playlist-backed Trending/Popular feeds

New config lists trending_playlists / popular_playlists. When set,
the feed serves the merged content of those local PUBLIC playlists
instead of the stock feed:

- Swap at the data layer (fetch_trending, popular_videos), so the
  HTML views and /api/v1/trending|popular emit the same items and
  API clients (Yattee, Materialious) need no changes.
- Playlists merge in config order, each in its own order,
  duplicates dropped. Missing or non-public entries are skipped
  and logged, never fatal.
- One local Postgres query per playlist — no YouTube call.
- PlaylistVideo converts to SearchVideo with neutral defaults for
  metadata a playlist row lacks (views, description, thumbnails).
- Trending category tabs and region are ignored while set. With a
  single trending playlist, 'View as playlist' links to it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

config/config.example.yml

@@ -391,6 +391,24 @@ https_only: false
 #    - 192.168.1.101
 #  logout_url: "https://auth.example.com/logout"
 
+##
+## Playlist-backed feeds (ArikTube extension).
+##
+## When set, the Trending and/or Popular feed serves the content of these
+## local PUBLIC playlists instead of the stock feed. Playlists merge in
+## the listed order, each in its own order, duplicates dropped. The swap
+## is at the data layer, so /api/v1/trending and /api/v1/popular serve
+## the same items — API clients need no changes. Missing or non-public
+## playlists are skipped and logged. Trending category tabs and region
+## are ignored while a list is set.
+##
+## Default: [] (stock feeds)
+##
+#trending_playlists:
+#  - IVPLxxxxxxxxxxxxxxxxxxxx
+#popular_playlists:
+#  - IVPLxxxxxxxxxxxxxxxxxxxx
+
 ##
 ## Enable/Disable the captcha challenge on the login page.
 ##

src/invidious.cr

@@ -193,6 +193,11 @@ Invidious::Jobs.register Invidious::Jobs::InstanceListRefreshJob.new
 Invidious::Jobs.start_all
 
 def popular_videos
+  # ArikTube: playlist-backed Popular
+  unless CONFIG.popular_playlists.empty?
+    return Invidious::PlaylistFeeds.feed_videos(CONFIG.popular_playlists)
+  end
+
   Invidious::Jobs::PullPopularVideosJob::POPULAR_VIDEOS.get
 end
 

src/invidious/config.cr

@@ -147,6 +147,11 @@ class Config
   # Subscribe to channels using PubSubHubbub (requires domain, hmac_key)
   property use_pubsub_feeds : Bool | Int32 = false
   property popular_enabled : Bool = true
+  # Playlist-backed feeds (ArikTube extension): when set, the Trending or
+  # Popular feed serves these local PUBLIC playlists (merged in order,
+  # duplicates dropped) instead of the stock feed content.
+  property trending_playlists : Array(String) = [] of String
+  property popular_playlists : Array(String) = [] of String
   property captcha_enabled : Bool = true
   property login_enabled : Bool = true
   property registration_enabled : Bool = true

src/invidious/playlist_feeds.cr

@@ -0,0 +1,58 @@
+# Playlist-backed Trending/Popular feeds (ArikTube extension).
+#
+# On a personal instance "Trending" and "Popular" mean "what this server's
+# owner pushes". When `trending_playlists` / `popular_playlists` name local
+# public playlists, those feeds serve the merged playlist content instead.
+# The swap happens at the data layer (fetch_trending / popular_videos), so
+# the HTML views and /api/v1/trending|popular emit the same items and every
+# API client shows them without client-side support.
+module Invidious::PlaylistFeeds
+  extend self
+
+  # Merged videos of the configured playlists: config order, each playlist
+  # in its own order, duplicates dropped. Missing or non-public playlists
+  # are skipped with a log line so one bad entry cannot break the feed.
+  def feed_videos(plids : Array(String)) : Array(SearchVideo)
+    videos = [] of SearchVideo
+    seen = Set(String).new
+
+    plids.each do |plid|
+      playlist = Invidious::Database::Playlists.select(id: plid)
+      if playlist.nil?
+        LOGGER.warn("PlaylistFeeds: playlist #{plid} does not exist, skipping")
+        next
+      end
+      if playlist.privacy != PlaylistPrivacy::Public
+        LOGGER.warn("PlaylistFeeds: playlist #{plid} is not public, skipping")
+        next
+      end
+
+      Invidious::Database::PlaylistVideos.select(plid, playlist.index, 0, limit: 200).each do |video|
+        next if seen.includes?(video.id)
+        seen << video.id
+        videos << as_search_video(video)
+      end
+    end
+
+    videos
+  end
+
+  # PlaylistVideo lacks views/description/thumbnails metadata; neutral
+  # defaults keep the SearchVideo JSON shape the feed endpoints promise.
+  private def as_search_video(video : PlaylistVideo) : SearchVideo
+    SearchVideo.new({
+      title:              video.title,
+      id:                 video.id,
+      author:             video.author,
+      ucid:               video.ucid,
+      published:          video.published,
+      views:              0_i64,
+      description_html:   "",
+      length_seconds:     video.length_seconds,
+      premiere_timestamp: nil,
+      author_verified:    false,
+      author_thumbnail:   nil,
+      badges:             video.live_now ? VideoBadges::LiveNow : VideoBadges::None,
+    })
+  end
+end

src/invidious/trending.cr

@@ -1,4 +1,12 @@
 def fetch_trending(trending_type, region, locale)
+  # ArikTube: playlist-backed Trending. Category tabs and region are
+  # ignored on purpose — the owner's list is the feed.
+  unless CONFIG.trending_playlists.empty?
+    plids = CONFIG.trending_playlists
+    plid = plids.size == 1 ? plids[0] : nil
+    return {Invidious::PlaylistFeeds.feed_videos(plids), plid}
+  end
+
   region ||= "US"
   region = region.upcase